Aortic cannula for ex vivo organ care system

ABSTRACT

The invention provides, in various embodiments, devices and methods relating to ex-vivo organ care. In certain embodiments, the invention relates to aortic cannulas for use in perfusion systems to return perfusate to the heart or delivering perfusate from the heart while the organ is sustained ex vivo at physiologic or near-physiologic conditions.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/258,194 filed Sep. 7, 2016 which claims the benefit of U.S.Provisional Application Ser. No. 62/215,825, titled “Aortic Cannula forEx Vivo Organ Care System,” filed Sep. 9, 2015. The specifications ofeach of the foregoing are incorporated by reference herein in theirentirety.

TECHNICAL FIELD

The present invention relates generally to medical devices and, inparticular, aortic cannulas for use in ex vivo organ care systems.Specifically the invention relates to aortic cannulas used to returnperfusate to the heart or delivering perfusate from the heart while theorgan is sustained ex vivo at physiologic or near-physiologicconditions.

BACKGROUND

Current organ preservation techniques typically involve hypothermicstorage of the organ in a chemical perfusate solution on ice. However,uses of conventional approaches results in injuries that increase as afunction of the length of time an organ is maintained ex-vivo. Thesetime restrictions limit the number of recipients who can be reached froma given donor site, thereby restricting the recipient pool for aharvested heart. Even within the few hour time limit, the heart maynevertheless be significantly damaged.

Effective preservation of an ex-vivo organ would also provide numerousother benefits. For instance, prolonged ex-vivo preservation wouldpermit more careful monitoring and functional testing of the harvestedorgan. This would in turn allow earlier detection and potential repairof defects in the harvested organ, further reducing the likelihood oftransplantation failure. The ability to perform simple repairs on theorgan would also allow many organs with minor defects to be saved,whereas current transplantation techniques require them to be discarded.In addition, more effective matching between the organ and a particularrecipient may be achieved, further reducing the likelihood of eventualorgan rejection.

Improved ex-vivo organ care has been achieved through the use of anex-vivo organ care system which maintains organs at physiologic ornear-physiologic conditions. Not only does the system maintain the organat physiologic temperatures, but in the case of the heart, the systemmaintains perfusate flow through the organ. In addition the systemmeasures and monitors electric stimulation in the heart. The ex vivoorgan care system where the heart sustained ex vivo at physiologic ornear-physiologic conditions are described in application Ser. No.11/822,495 entitled “Systems for monitoring and applying electricalcurrents in an organ perfusion system,” U.S. Pat. No. 8,304,181 entitled“Method for ex-vivo organ care and for using lactate as an indication ofdonor organ status,” and U.S. Pat. No. 8,409,846 entitled “Compositions,methods and devices for maintaining an organ,” which are incorporatedherein by reference.

To maintain physiologic or near-physiologic perfusate flow through theheart, the organ must interface with the system via the aorta. Thisinterface is achieved via an aortic cannula. Current aortic cannuladesigns lead to organ slippage, difficulties in maintaining a liquidtight seal, and damage to the aorta. Often these designs rely solelyupon a cable tie in contact with the aorta to tighten the aorta to theaortic cannula. Depending on the size of the aorta and the size of theaortic cannula, there is a risk of laceration due to the cable tiesexerting too much tension on aortic tissue, or the risk of leakage ifthey do not exert sufficient tension. Thus, there exists a need for anaortic cannula that is easy for health care workers to deploy, creates atight seal with the aorta, reduces aortic slipping, and causes minimaldamage to the aorta.

In view of the foregoing, improved devices for attaching the aorta tothe system and methods of use in ex vivo organ care systems are needed.

SUMMARY

In one embodiment the invention includes an aortic cannula for use withan ex vivo organ care system and methods of using the same. One aspectof the invention includes an aortic cannula comprising, a cannula bodywhich further comprises, a fitting adapted to connect to an organ caresystem, an aorta interface to contact an aorta, and a pivot arm strapoperably connected to a pivot mount, wherein the pivot mount allows thepivot arm strap to uniformly contact the aorta to hold the aorta on theaorta interface. In one embodiment, the aortic cannula further comprisesa pivot arm connected to the pivot arm strap and to the pivot mount,such that when the pivot arm is moved toward the cannula body byrotation around the pivot mount the pivot arm strap moves away from thecannula body. In another embodiment of the aortic cannula the pivot armand the pivot arm strap are parts of a single piece. In anotherembodiment, the aortic cannula comprises a spring which applies pressureto the pivot arm strap to hold the aorta on the aorta interface. Inanother embodiment of the aortic cannula a dowel pin communicates withthe spring to allow the pivot arm to rotate around the dowel pin. Inanother embodiment of the aortic cannula the pivot arm further comprisesa grip pad used to depress the top of the pivot arm. In anotherembodiment of the aortic cannula the grip pad is textured. In anotherembodiment of the aortic cannula the grip pad is removable. In anotherembodiment of the aortic cannula the pivot arm straps further comprise aloop and guide which retain a cable tie around the pivot arm strap. Inanother embodiment, the aortic cannula further comprises windows sizedto normalize the compression exerted on the aorta by the cable tie suchthat the same amount of pressure will be exerted on the aorta regardlessof the size of the pivot arm strap for a given cable tie tension. Inanother embodiment, the aortic cannula further comprises a connectorused to reversibly secure the aortic cannula to an organ chamber. Inanother embodiment of the aortic cannula the connector is a threadedlocking nut. In another embodiment of the aortic cannula the aortainterface is textured.

One aspect of the invention includes a method of using an aortic cannulato place a heart in fluid communication with an organ care system themethod comprising, selecting an aortic cannula sized to fit the aorta ofthe heart the aortic cannula comprising, a cannula body furthercomprising, a fitting adapted to connect to an organ care system, anaorta interface to contact an aorta, and a pivot arm strap operablyconnected to a pivot mount, wherein the pivot mount allows the pivot armstrap to uniformly contact the aorta to hold the aorta on the aortainterface, depressing the pivot arm such that it rotates around thedowel pin and the pivot arm strap moves away from the cannula body,placing the cannula in the aorta, releasing the pivot arm, tightening acable tie around the pivot arm strap to hold the aorta in place, andinserting the tapered fitting into an organ care system. In oneembodiment, the method further comprises the step of suturing surgicalfelt pledgets on the aorta before placing the aorta on the aorticcannula.

BRIEF DESCRIPTION OF THE FIGURES

The following figures depict illustrative embodiments of the invention.

FIG. 1 illustrates a diagram depicting an aortic cannula in oneembodiment.

FIG. 2a illustrates a side view of a cannula body in one embodiment.

FIG. 2b illustrates a side view of a cannula body and a spring pocketaccording to one embodiment.

FIG. 2c illustrates a side view of a cannula body in one embodiment.

FIG. 3a illustrates one embodiment of a pivot arm.

FIG. 3b illustrates a side view of a pivot arm and strap according toone embodiment.

FIG. 3c illustrates another view of a pivot arm and strap according toone embodiment.

FIG. 3d illustrates another view of a pivot arm and strap according toone embodiment.

FIG. 3e illustrates a top view of a pivot arm and strap according to oneembodiment.

FIG. 4 illustrates a diagram showing the shape of a cannula body texturein one embodiment.

FIG. 5 illustrates a top view of a pivot mount according to oneembodiment.

FIG. 6 illustrates a tip holder according to one embodiment.

DETAILED DESCRIPTION Cannula Body

FIG. 1 is a diagram depicting the aortic cannula 100 in one embodiment.The aortic cannula device 100 comprises a cannula body 114, a lockingnut 102, and a pivot arm 140. The cannula body 114 may contain threesub-sections, a tapered fitting 108, a tapered midsection 130 and anaorta interface 132. These subsections can be seen in FIG. 1 as well asin various side views of the cannula body 114 depicted in FIGS. 2a-2b .In one embodiment, the cannula body 114 is made from injection moldedclear polycarbonate. However, one of skill in the art would understandthat the cannula body can be made from other types of plastic or anyother suitable material.

One of skill in the art would recognize that the while the shape of thecannula body 114 should be generally cylindrical, the opening need notbe perfectly circular. The three sub-sections, tapered fitting 108,tapered midsection 130, and aorta interface 132, may be of differentlengths relative to one another. In addition the different subsectionsmay be made from one piece and they may have the same diameter. One ofskill in the art would also recognize that the taper angle in thesub-sections, tapered fitting 108, tapered midsection 130, and aortainterface 132, may vary so long as the aorta interface reaches adiameter within the typical range of the diameter of an human aorta.

One end of the aortic cannula 100 forms tapered fitting 108. The taperedfitting is sized to couple to a female connector on an organ chamber(not shown) to create a seal. A threaded locking nut 102, pictured inFIG. 1, is used to reversibly secure the aortic cannula 100 to the organchamber (not shown). In one embodiment, the locking nut 102 has fourwings 104 extending from its outer surface that are used for grippingand turning the locking nut 102. In one embodiment the wings 104 arerectangular. One of skill in the art would understand that the wings 104could be any shape or omitted. The locking nut 102 may have a lipprotruding inward from its bottom edge that snaps over locking ridge 110and into the locking groove 112 on the cannula body 114. The lockinggroove 112 and the locking ridge 110 can be seen in FIG. 1 and FIGS.2a-2b . Alternatively, the locking nut 102 may be secured to the cannulabody 114 using other mechanisms known to one skilled in the art. Oncethe locking nut 102 is seated in the locking groove 112, the aorticcannula 100 is securely fastened to the organ chamber (not shown) byturning the locking nut 102. Perfusate can be perfused through thecannula into the heart without leaking. One of skill in the art wouldunderstand that other designs can be used to attach the aortic cannula100 to the organ chamber to prevent leakage.

One of skill in the art would understand that the aortic cannula 100 canbe connected to an organ care system or any other tube, device, or pathof flow. In addition, one of skill in the art would appreciate that thelocking nut 102 may be omitted in embodiments where the male-femaleconnection between the aortic cannula 100 and the organ care system (notshown) is tight enough to prevent leakage. One of skill in the art wouldalso recognize that the locking nut 102 could be replaced with othertypes of connectors generally used in the art to create a flow pathbetween two tubes.

The tapered midsection 130 extends from the bottom edge of the taperedfitting 108 to the top edge of the aorta interface 132. The taperedmidsection 130 reaches a final diameter the size of the aorta interface132. The tapered midsection 130 helps to ensure smooth fluid flow fromthe aorta interface 132 to the tapered fitting 108. The taperedmidsection 130 also helps minimize air trap and hemolysis and improvehemodynamics due to the smooth transition in flow path. The taperedmidsection 130 has a pivot mount 122 and a spring pocket 106. The pivotmount 122 and the spring pocket 106 may be integrated with the taperedmidsection 130. In one embodiment, the tapered midsection 130 has twopivot mounts 122 and two spring pockets 106, shown in FIGS. 1 and 2 b.The pivot mounts 122 are located on each side of the cannula body 114.One of ordinary skill in the art would understand that one or more pivotmounts 122 and spring pockets 106 could be used. As shown in FIG. 5, inone embodiment the pivot mount 122 has a circular center hole 138 sizedto receive a dowel pin 120. The spring pocket 106 is located on thecannula body 114 and provides a space for a torsional spring (notshown). The dowel pin 120 fits through one side of the center hole 138on the integrated pivot mount 122, through the center of the torsionalspring in the spring pocket 106, and through the other side of thecenter hole 138 on the integrated pivot mount 122. The torsional springis oriented in spring pocket 106 such that depressing the pivot armcompresses the spring. One end of the torsional spring rests in thespring end pocket 134 on the thumb pad 116 seen in FIG. 3a . One ofordinary skill in the art would understand that there are various waysto attach the pivot mount 122 to the cannula body 114 that allows thepivot mount 122 to pivot or move so that the aorta can be fit onto thecannula body 114 in operation. In one embodiment, the pivot mount 122 ismade from injection molded polycarbonate, acetyl, or any suitablematerial.

One of skill in the art would also recognize that the torsional springcould be replaced with other types of spring loading mechanisms oromitted completely. The torsional spring could also be replaced by amolded leaf spring on the pivot arm or on the grip pad. With the use ofa molded leaf spring the dowel pin would be omitted and cylindricalbosses on the cannula body 114 or a similar structure could be used toperform the same function.

The aorta interface 132 is located adjacent the tapered midsection 130.The aorta interface 132 may be of a constant diameter and sized to fitwithin the aorta. The diameter of the aorta interface 132 can be between0.5 and 2 inches. In some embodiments the diameter of the aortainterface 132 can be between 0.75 and 1.125 inches. Preferably, in someembodiments the diameter of the aorta interface is 0.75 inches, 0.875inches, 1 inch, or 1.125 inches. The aorta interface 132 may be smoothor textured. FIG. 1 illustrates a texture 128 on the aorta interface 132to help prevent the aorta from slipping off of the cannula body 114. Inthe embodiment shown in FIG. 1, the aortic cannula 100 is placed in theaorta so that the aorta does not rise above the end of the texture 128.FIG. 4 is a cross sectional view of one embodiment of the texture 128.The texture 128 may be of any shape. In one embodiment the texture 128comprises concentric ridges extending around the aorta interface 132that are sloped at a 45 degree angle on their lower side and areperpendicular to the cannula body 114 on their upper face. This designallows the aorta to slide onto the aorta interface 132 easily, butprevents the aorta from sliding off the aorta interface 132. Preferablythe ridges are about 0.005 inches tall. However, one of skill in the artwould understand that the texture features could be of any shape andsize to allow the aorta to be situated around the aorta interface 132and to help hold the aorta in place while minimizing damage to thetissue. In one embodiment, the radial edge of the aortic interface 132does not have a ridge to minimize trauma to the tissue. Alternatively,one of skill in the art would recognize that a ridge could be designedto minimize tissue trauma and to hold the aorta in place.

Pivot Arm

A pivot arm 140 is coupled to the pivot mount 122. FIGS. 3a-e illustratedifferent views of a pivot arm and pivot arm strap (discussed below) inone embodiment. The pivot arm 140 allows the device 100 to adjust andgrip aortas of different thicknesses. In one embodiment the cannula body114 includes two pivot arms 140 coupled to two pivot mounts 122 on thecannula body. One of ordinary skill would understand that the number ofpivot arms 140 corresponds to the number of pivot mounts 122. The pivotarm 140 comprises a grip pad 116, a sliding pivot window 118, and astrap 124. The sliding pivot window 118 allows the strap 124 to maintainuniform contact with the aorta through a range of motion. The grip pad116 can be smooth, or contain features such as molded ridges or othertexture to stop the user's fingers from slipping. The grip pad can beany shape, preferably round. In some embodiments the grip pad 116 may bedetachable. In other embodiments a reusable tool that attaches to thepivot arms 140 could be used in place of the grip pads 116. The dowelpin 120 allows the pivot arm 140 to rotate around the dowel pin 120 whenit is actuated. The pivot arm 140 is made from injection molded acetylor any material with similar properties. One of skill in the art wouldrecognize that while the sliding pivot provides certain advantages overa fixed pivot point, a fixed pivot point could also be used. Someembodiments may include a locking mechanism to hold the pivot arm 140 inan open position.

Pivot Arm Strap

The pivot arm strap 124 is coupled to the pivot arm 140. The pivot armstrap is best seen in FIGS. 1 and 3. As shown in FIG. 1, in oneembodiment the cannula body 114 includes two pivot arm straps 124coupled to two pivot arms 140. One of ordinary skill would understandthat the number of pivot straps 124 corresponds to the number of pivotarms 140. The pivot arm strap 124 and the sliding pivot window 118 allowthe cannula body 114 to uniformly grip the aorta. The pivot arm strap124 is designed to be stiff enough to hold the aorta, while maintainingenough flexibility to conform to the aorta and minimize tissue damage.The pivot arm straps 124 are curved. The pivot arm strap 124 optionallyhas a loop 136 and a guide 142 to retain a cable tie (not shown) aroundthe pivot arm strap 124. The cable tie is made from a flexible nylonmaterial or material with similar properties. Once the cable tie hasbeen threaded through the loop 136 and slotted in the guide 142, it istightened to the desired tension. The amount that the cable tie istightened is the same for all sizes of cannulas. Windows 126 in thepivot arm strap 124 normalize the pressure exerted on the aorta byaltering the surface area of the strap in contact with the aorta.Accordingly, the size of the windows 126 vary depending on the size ofthe aorta. The size of the windows 126 are calculated so that when thecable tie is tightened, it exerts the same compression on the aorta forevery size device 100. Thus, the compression exerted on the aorta holdsit in place without damaging the tissue. One of ordinary skill wouldunderstand that alternatively, the cable tie may be tightened to aspecific tension for each size of the device 100. In addition, othermechanisms of clamping to hold the aorta in place could be used in placeof the cable tie, for example a hose clamp or a tension strap.Additionally, the pivot arm strap 124 and the windows 126 could be ofdifferent shapes and sizes. Alternatively, the windows could be omitted.One of skill in the art would also understand that the pivot arm 140 andthe pivot arm strap 124 could be sections of a single piece. Inaddition, one of skill in the art would understand that the innersurface of the pivot arm strap 124 could be smooth, or textured foradditional traction.

In one embodiment, the aorta is secured to the cannula body. The grippad 116 is depressed by the user causing the pivot arm 140 to movearound the sliding pivot window 118 and to compress torsional spring.The pivot arm 140 rotates around the dowel pin 120 in the sliding pivotwindow 118 and the pivot arm straps 124 move away from the cannula body114, which makes room to place the cannula in the aorta in a preferredmanner than if the pivot point were fixed. When the grip pad 116 isreleased the torsional spring (not shown) exerts pressure on the pivotarm strap 124 and temporarily holds the aorta in place. The strapscloses on the aorta and the sliding pivot window 118 allows the pivotpoint to change in order to compensate for variations in tissuethickness and maintain alignment and concentricity of pivot arm 140 tocannula body 114 through the full range of rotation. This allows thestrap 124 to seat uniformly on the aorta. Then, the cable tie isthreaded through the loop 136 and between the guide 142. The cable tieis tightened to a predetermined tension. One of skill in the art wouldunderstand that the cable tie could be replaced with other mechanismsfor securing the pivot arm straps 124. In some embodiments the cable tiecan come preassembled in the loops 136.

Pledgets

In some embodiments, the user may suture surgical felt pledgets on theaorta. The pledgets serve as an additional measure to retain the aortaon the cannula body 114 because the pledgets provide a barrier that doesnot slide between the pivot arm strap 124 and the cannula body 114. Foursets of two (one inside, one outside) pledgets are equally spaced aroundthe aorta and sutured. One of skill in the art will recognize that moreor fewer pledgets may be used. In one embodiment, the aorta ispositioned onto the cannula body 114 so that the pledgets are notdirectly above a space between the pivot arms 140 to prevent thepledgets from sliding through the space between the two sides of thepivot arm straps 124. It will be recognized by one of skill in the artthat the pledgets may be placed anywhere on the aorta and end up in anyorientation with respect to the pivot arm straps. The pledgets may bestandard, surgical felt pledgets. Alternatively, they may be injectedmolded, rigid, elastomeric pledgets made of a high Durometer material,such as silicone, or a similar material. One of skill in the art wouldunderstand that the pledgets could be replaced with other materials thatattach to the tissue, and that provide an anchor to prevent the devicefrom sliding between the strap and the cannula body or damaging thetissue. Examples of these materials include, but are not limited to, acontinuous ring of material that attaches to the tissue or a staple.

Tip Holder

FIG. 6 depicts a tip holder 601. The tip holder 601 is generallycylindrical, though it may have other shapes. The tip holder has ahandle 603. The handle may take any shape that allows a user to hold thetip holder 601. The tip holder 601 can also have threads 602. Thelocking nut 102 can be screwed onto the threads 602. The tip holder 601can also have a stopper 604 which protrudes from the tip holder 601 andserves as a stopping point for the locking nut 102. One of skill in theart would understand that other designs can be used to attach thelocking nut to the tip holder. Alternatively, the tip holder may besecured to the aortic cannula 100 using other mechanisms known to oneskilled in the art. Once secured, the tip holder can be used to hold theaortic cannula 100 with or without a heart positioned on the aorticcannula 100.

Example 1

The aortic cannula 100 may be used to connect a heart to an organchamber (not shown). The aortic cannula 100 holds the aorta open and inplace and allows perfusate to be perfused through the heart so the heartcan be maintained in near physiologic conditions. In one embodiment, todeploy the aortic cannula, the user first selects an aortic cannula 100that is sized to fit the heart. In one embodiment the aortic cannula 100may be selected by measuring the aorta. The user depresses the thumbpads 116 on the spring-loaded pivot arms. When the user depresses thegrip pads 116, the pivot arms 140 rotate around the dowel pin 120 withinthe sliding pivot window 118 and the pivot arm straps 124 move away fromthe cannula body 114 making room to place the cannula in the aorta. Theuser can place the cannula in the aorta. Then the user releases thethumb pads allowing the pivot arms 140 to close on the aorta. The pivotarms 140 may be operated at the same time or individually. The pressurecreated by the torsional springs temporarily holds the aorta in place.The user may adjust the aorta position, if necessary, such that aorta isfully engaged on the cannula body 114. Next the user places a cable tiethrough the loops 136 and guides 142 in the pivot arm straps 124. Theuser then tightens the cable tie to hold the aorta in place. In someembodiments the cable tie may be tightened using a tool which tightensthe cable tie to a predetermined force. The user inserts the taperedfitting 108 into the organ chamber (not shown). Then the user tightensthe locking nut 102. One of skill in the art will recognize that in someembodiments the aortic cannula 100 could first be seated in the organchamber and then the aorta could be secured to the aortic cannula 100.

1. An aortic cannula for use in an ex vivo organ care system comprising:a cannula body comprising: a fitting adapted to connect to an organ caresystem, and an aorta interface to contact an aorta; and a pivot armstrap operably connected to a pivot mount, wherein the pivot mountallows the pivot arm strap to uniformly contact the aorta to hold theaorta on the aorta interface.